Cooled mirrors

ABSTRACT

Optical mirrors are provided, particularly for use as lasercavity mirrors, including a face plate having an optically reflective surface in heat-exchanging relationship with coolant passages in which the flow of coolant in adjacent coolant passages is preferably counter-current in order to cool the optically reflective surface in a thermally balanced manner. Coolant is distributed to and collected from the coolant passages in the face plate by a first manifold plate. The first manifold plate has coolant distribution and collection passages for distributing coolant to and collecting coolant from the coolant passages in the face plate and manifold means for receiving and distributing coolant to each of the coolant distribution passages in the first manifold plate. The coolant collected by the coolant collection passages in the first manifold plate is distributed to coolant collection passages formed in a second manifold plate. Manifold means in the second manifold plate are provided for receiving coolant from each of the coolant collection passages in the second manifold plate and for conducting the coolant exteriorly of the mirror.

United States Patent 091 Sorensen et al. 1

[ 1, Jan. 2, 1973 [54] COOLEDAMIRRORS' [75] Inventors: Ronald L.Sorensen, Thousand sworth, both of Calif.

[73] Assignee:

' tion Filed: April 2, 1971 Appl. No.: 130,744

US. Cl "350/310, 165/61 Int. Cl. ..G02b 7/18 Field of Search ..350/288,310, 61-67, 350/299, 179', 311, 312, 318, 319, 93, 63; 165/61 ReferencesCited UNITED STATES PATENTS l/l970 Evoy ..350/3l0 7/1971 Smillie....3/1925 Thomson Primary Examiner-David Schonberg AssistantExaminerMichael J. Tokar Att0rneyL. Lee Humphries, Thomas S. MacDonaldand D. Douglas Price Oaks; Charlton Dunn, 11], Chat-' North AmericanRockwell Corpora- [5 7] ABSTRACT Optical mirrors are provided,particularly for use as laser-cavity mirrors, including ,a face platehaving an optically reflective surface in heat-exchanging relationshipwith coolant passages'in which the flow of coolant in adjacent coolantpassages is preferably counter-current in order to cool the opticallyreflective surface in a thermally balanced manner. Coolant isdistributed to and collected from thecoolant passages in the face plateby a first manifold plate. The first manifold plate has coolantdistribution and collection passagesfor distributing coolant to andcollecting coolant from the coolant passages in the face plate andmanifold means for receiving and distributing coolant to each of thecoolant distribution passages in the first manifold plate. The coolantcollec ted by the coolant collection passages in the first manifoldplate is distributed to coolant collection passages formed in a secondmanifold plate. Manifold means in the second manifold plate are providedfor receiving coolant'from each of the coolant collection passagesin thesecond manifold plate and for con ducting the coolant exteriorly of themirror.

14 Claims, 4 Drawing Figures PATENTEDJAH' 2197a SHEET 1 BF 3 8 4 4 0 0 33 2 2 4 v 4 4 4 5 M. W... 4 4

34 INVENTORS.

RONALD L. SORENSEN CHARLTON DUNN m ATTORNEY PATENTED A 21975 3.708.223

SHEET 2 OF 3 IN VE N TORS RONALD L. SORENSEN BY CHARLTON DUNN III ssqkmATTORNEY P'A'IENTEBJAM 2191 3.708.223 SHEET 3 [1F 3 g INVENTORS. N;RONALD 1.. SORENSEN BY CHARLTON DUNN m 'sag am em ATTORNEY COOLEDMIRRORS BACKGROUND OF THE INVENTION Cooled mirrors are required inapplications in which a high heat flux exists at the opticallyreflective surface of the mirror and in which only minimal thermaldistortion of the optically reflective surface can be permitted.Laser-cavity mirrors, and particularly mirrors for highpowered,continuous wave lasers, are typical of mirrors which may require coolingin order to function properly. For example, surface flatness inlaser-cavity mirrors is often specified to be within 1/10 or I/20 of awave length of light and frequently to be within 1/100 of a wave lengthof light. In other words, deviations from perfect flatness may representless than 1] 1,000,000 of an inch. The heat flux at the opticallyreflective surface of a laser-cavity mirror is typically within therange of to I00 watts/cm or higher for many conventional lasers (e.g.,continuous wave CO lasers). Accordingly, cooling of the laser-cavitymirrors may be required in order to maintain the stringent surfaceflatness requirements of the mirrors under the high heat fluxes presentat the optically reflective surface.

Laser-cavity mirrors are mirrors used in a laser optical cavity. A laseroptical cavity typically comprises a cylindrical region located betweentwo opposing plane parallel or curved mirrors located at right angles tothe axis of the cylindrical region. The cylindrical region may be acrystal or gas envelope in which lasing action takes place. One of themirrors is required to be partially transmissive in order to extract auseful beam of coherent light from the optical cavity. The dimensioningof laser-cavity mirrors and the location of the mirrors with respect tothe cylindrical region in which the lasing action takes place is wellknown in the art. See, for example, an article entitled, Lasers, in theAmerican Scientist, volume 51, No. 1, March 1963 with respect to lasersin general and with respect to the provision and location oflaser-cavity mirrors.

SUMMARY OF THE INVENTION Optical mirrors are provided, particularly foruse as laser-cavity mirrors, including a first component having coolantdistribution and collection passages and manifold means for receivingand distributing coolant to each of the coolant distribution passages. Asecond component is then provided having an optically reflective surfaceand coolant passages in heat-exchanging relationship with the opticallyreflective surface. Each of the coolant passages in the second componentis in coolant flow communication with one of the coolant distributionand one of the coolant collection passages in the first component. A.third component is then provided having coolant collection passages andmanifold means for collecting coolant from each of the coolantcollection passages in the third component and for discharging coolantfrom the mirror. The coolant collection passages in the third componentare in coolant flow communication with the coolant collection passagesin the first component.

The first component of the mirror is preferably a first manifold platein which the coolant distribution and collection passages are formed ina first face of the manifold plate. At least a portion of each of thecoolant distribution and collection passages in the first face of thefirst manifold plate extend through the first manifold plate. The secondcomponent is preferably a face plate in which the coolant passages areformed in a first face of the face plate and the optically reflectivesurface is formed on a second face of the face plate.

The third component is preferably a second manifold plate in which thecoolant collection passages and the manifold means are formed in a firstface of the second manifold plate.- At least a portion of each of thecoolant collection passages in the first face of the second manifoldplate extend through the second manifold plate. The face plate is bondedto and mated with the first manifold plate such that the coolantpassages in the face plate are in coolant flow communication with theportions of the coolant distribution and collection passages extendingthrough the first manifold plate and such that the second face of thefirst manifold plate acts as a closure for the coolant passages in thefirst face of the face plate. The face plate is preferably mated withthe first manifold plate such that the flow of coolant in adjacentcoolant passages in the face plate is countercurrent in order to coolthe optically reflective surface of the face plate in a'thermallybalanced manner. Thev second manifold plate is bonded to and mated withthe first manifold plate such that the portions of the coolantcollection passages extending through the second manifold plate are incoolant flow communication with the coolant collection passages in thefirst manifold plate and such that the second face of the secondmanifold plate acts as a closure for the coolant passages and manifoldmeans in the first face of the first manifold plate.

Accordingly, it is an object of the present invention to provide amirror which has coolant flow passages and manifold means formed thereinfor cooling the optically reflective surface of the mirror.

A further object of the present invention is to provide a mirror inwhich the optically reflective surface of the mirror is cooled in athermally balanced manner by providing countercurrent coolant flow inadjacent coolant passages on the back side of the optically reflectivesurface of the face plate of the mirror.

A further object of the present invention is the provision of thermallybalanced, cooled mirrors which are suitable for use as lasercavitymirrors.

Further objects and advantages of the present invention will becomeapparent upon reading the undergoing specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cut-away,perspective view of a thermally balanced,.cooled mirror of the presentinvention.

FIG. 2 is an exploded, perspective view of the mirror of FIG. 1. FIG. 3is a partially cut-away, perspective view of a partially transmissive,thermally balanced, cooled mir- DESCRIPTION OF THE PREFERRED EMBODIMENTSThe present invention is directed to optical mirrors preferablycomprising a face and an a first manifold plate, a second manifold plateand a closure plate. The

first manifold plate has coolant distribution and collec tion passages,which are generally parallel, longitudinal slots, formed in a first faceof the first manifold plate. At leasta portion of each of the coolantdistribution and collection passages extends through the first manifoldplatejManifold means are formed in the first face of the first manifoldplate for receiving and distributing coolant to each of the coolantdistribution passages in the first manifold plate.

Coolant passages are formed in a first face of the face plate and anoptically reflective surface is formed on the second face. The coolantpassages and the optically reflective surface in the face plate are inheat-exchanging relationship. The coolant passages are generallyparallel, longitudinal slots formed on the back side of the opticallyreflective surface of the face plate. The face plate is bonded to thefirst manifold plate such as by diffusion bonding. The face plate ismated with the first manifold plate such that the coolant passages inthe face plate are in coolant flow communication with the portions ofthe coolant distribution and collection passages extending through thefirst manifold plate. The face plate is also mated with the firstmanifold plate such that the second face of the first manifold plateacts as a closure for the coolant passages in the first face of the faceplate. Each of the coolant passages in the face plate is in coolant flowcommunication with a corresponding one of the coolant distribution and acorresponding one of the coolant collection passages in the firstmanifold plate. The coolant passages in the face plate and the coolantdistribution and collection passages in the first manifold plate arepreferably arranged and mated such that the flow of coolant in adjacentcoolant passages in the face plate is countercurrent or, in other words,is in opposite directions in order to cool the optically reflectivesurface of the face plate in a thermally balanced manner.

The second manifold plate has coolant collection passages formed in afirst face of the second manifold plate. At least a portion of each ofthe coolant collection passages extends through the second manifoldplate. Manifold means, for collecting coolant from each of the coolantcollection passages in the second manifold plate and for'dischargingcoolant from the mirror, are formed in the first face of the secondmanifold plate. The second manifold plate is bonded to the firstmanifold plate suchas by diffus'ionbonding. Thesecond' manifold plate ismated with the first manifold plate such that the portions of thecoolant collection passages extending through the second manifold plateare in coolant flow communication with the coolant collection passagesin the first manifold plate. The second manifold plate is also matedwith the first manifold plate such that the second face of the 'secondmanifold plate acts as a closure for the coolant passages and manifoldmeans in the first face in the first manifold plate.

The closure plate acts'as a closure for the coolant collection passagesand the manifold means in the first face'of the second manifold plateand may also optionally provide inlet and exit means for the passage ofcoolant into and out of the mirror.

Referring now in detail to FIGS. 1 and 2, closure plate 12 in mirrorcontains inlet means 14, shown as the coolant distribution network ofmirror 10. Manifold plate 16 contains inlet means 18, shown asv acircular aperture, which is in coolant fow communication with inletmeans 14 in closure plate 12 and withmanifold means 20 in manifold plate22. inlet means 14 and 18 are of the same shape and are axially alignedso that no loss of coolant occurs to the interior of mirror 10. lnletmeans 18 mates with manifold means 20 so that all of the coolant fluidpassed through inlet means 18 is communicated to manifold means 20.Manifold ineans 20, shown as a curved channel, is formed in face- 24 ofmanifold plate 22. Manifold means 20 is in coolant flow communicationwith each of coolant distribution passages 26 in manifold plate 22. Theexact shape of manifold means 20 is not critical except that manifoldmeans 20 should approximately equally distribute the inlet coolant flowfrom inlet means 18 between each of coolant distribution passages 26.

Coolant distribution passages 26, shown as parallel, longitudinal,equally spaced slots, are formed in upper side 28 and'lower side 30 offace 24 of manifold plate 22. The upper end of each of coolantdistribution passages 26 in upper side 28 and the lower end of each ofcoolant distribution passages 26 in lower side 30'of manifold plate 22extends through manifold plate 22 from face 24 to face 31. Coolantdistribution passages 26 are cut across or machined across upper andlower edges 32 and 33, respectively, of manifold plate 22. Each of theends of coolant distribution passages 26 extending through manifoldplate 22 is mated with and is in coolant flow communication with one ofthe ends of a coolant passage 34 in face plate 36. However, none ofcoolant distribution passages 26 are in coolant flow communication withmore than one of coolant passages 34 in face plate 36.

Coolant passages 34, shown as parallel, longitudinal, equally spacedslots, are formed in face 38 of face plate 36. The exact shape andconfiguration of coolant passages 34 is notcritical; however, coolantpassages 34 should be arranged to evenly cool optically reflective face40 of face plate 36. Each of coolant passages 34 in face plate 36 ismated with and is in coolant-flow communication with one of coolantdistribution passages 26 and one of coolant collection passages 42 inmanifold plate 22. One of each adjacent pairof coolant passages 34 inface plate 36 is in coolant flow communication with a coolantdistribution passage 26 in upper side 28 and a coolant collectionpassage 42 in lower side 30 of face 24 of manifold plate 22 and theother coolant-passage of the adjacent pair of coolant passages 34 is incoolant flow communication with a coolant collection passage 42 in upperside 28 and a coolant distribution passage 26 in lower side 30 of face24 of manifold plate 22. Accordingly, coolant flow is countercurrent or,in other words, .is in opposite directions in adjacent coolant passages34 in faceplate Adjacent coolant distribution passages 26 and coolantcollection passages 42 in manifold plate 22 are in coolant flowcommunication with the ends of adjacent coolant passages 34 in' faceplate 36. Adjacent coolant distribution-passages 26 in manifold plate 22are in coolant flow communication with the ends of subadjacent coolantpassages 34 in face plate 36. In like manner, adjacent coolantcollection passages 42 in manifold plate 22 are in coolant flowcommunication with the ends of subadjacent coolant passages 34 in faceplate 36. The term subadjacent" is used herein to mean a coolant passagewhich immediately follows oris immediately adjacent to an adjacentcoolant passage.

1 dinal center lines of, the lands 54 which are formed by Face plate 36is bonded to and mated with manifold plate 22 such that face 31 ofmanifold plate 22 acts as a closure for coolant passages 34 in faceplate 36. Heat is evenly distributed to face 31 of manifold plate 22 bycoolant flowing in coolant passages 34 in face plate 36. This evenheating of face 31 of manifold plate 22 helps minimize the thermaldistortion of optically reflective face 40 of face plate 36 which wouldbe caused by the uneven thermal expansion of face plate 36 relative tomanifold plate 22. Coolant is only communication between manifold plate22 and face plate 36 via coolant distribution passages 26 and coolantcollection passages 42 and the ends of coolant passages 34.

Coolant collection passages 42, shown as parallel, longitudinal, equallyspaced slots, are formed in upper side 28 and lower side 30 of face 24of manifold plate 22 and extend through manifold plate 22'from face 24to face 31. Coolant collection passages 42 are cut across or machinedacross upper and lower edges 32 and 33, respectively, of manifold plate22. 8

One of each adjacent pair of coolant passages in manifold plate 22 is acoolant distribution passage 26 and the other coolant passage of eachadjacent pair is a coolant collection passage 42. Each coolantdistribution passage 26 in upper side 28 of face 24 of manifold plate 22is on the same longitudinal axis of face 24 of manifold plate 22 as acoolant collection passage 42 in lower side 30 of face 24 of manifoldplate 22. In like manner, each coolant collection passage 42 in upperside 28 of face 24 of manifold plate 22 is on the same longitudinal axisof face 24 of manifold plate 22 as a coolant distribution passage 26 inlower side 30 of face 24 of manifold plate 22. Each of coolantcollection passages 42 in manifold plate 22 is in coolant flowcommunication with a coolant collection passage 44 in manifold plate 16.

Coolant collection passages 44, shown as parallel, longitudinal, equallyspaced slots, are formed in upper side 46 and lower side 48 of face 50of manifold plate 16. The upper end of each of coolant collectionpassages 44 in upper side 46 and the lower end of each of coolantcollection passages 44 in lower side 48 of face 50 of manifold plate 16extends through manifold plate 16 from face 50 to face 51. Coolantcollection passages 44 are cut or machined across the upper and loweredges 52 and 53, respectively, of manifold plate 16. Each of the ends ofcoolant collection passages 44 extending through manifold plate 16 ismated with and is in coolant flow communication with oneof coolantcollection passages 42 in manifold plate 22. Each of coolant collectionpassages 44 inupperside 46 of face 50 of manifold plate 16 is in coolantflow communication with one of coolant collection passages 42 in upperside 28 of face 24 of manifold plate 22. In like manner, each of coolantcollection passages 44 in lower side 48 of face 50 of manifold plate 16is in coolant flow communication with one of coolant collection passages42 in lower side 30 of face 24 of manifold plate 22. Adjacent coolantcollection passages in manifold plate 16 are in coolant flowcommunication with adjacent coolant collection passages 42 in manifoldplate 22.

The coolant collection passages 44 in upper side 46 of face 50 ofmanifold plate 16 are on the same longitudinal axis of face 50 ofmanifold plate 16 as the longituadjacent coolant collection passages 44in lower side 48 of face 50 of manifold plate 16. In like manner,coolant collection passages 44 in lower side 48 of face 50 of manifoldplate 16 are on the same longitudinal axis of face 50 of manifold plate16 as the longitudinal center lines of the lands 56 which are formed byadjacent coolant collection passages 44 in upper side 46 of face 50 ofmanifold plate 16.

Manifold plate 16 is bonded to and mated with manifold plate 22 suchthat face 51 of manifold plate 16 acts as a closure for manifold means20 and coolant distribution passages 26 in face 24 of manifold plate 22.Coolant flowing in manifold means 20 and coolant distribution passages26 in manifold plate 22 is heated by heat transferred from face 31 ofmanifold plate 22. This heat is then transferred by the coolant to face51 of manifold plate 16. Coolant collection passages 44 in manifoldplate 16 are in coolant flow communication with manifold means 58 inmanifold plate 16. Manifold means 58, shown as a curved channel, isformed in face 50 of manifold plate 16. The exact shape of manifoldmeans 58 is not critical except that manifold means 58 should collectcoolant from each of coolant collection passages 44 and conduct thiscoolant to exit means 60.

Closure plate 12 contains exit means 60, shown as a circular aperture,for discharging coolant from mirror 10. Exit means 60 mates withmanifold means58 such that no loss of coolant occurs to the interior ofmirror 10. Closure plate 12 is mated with manifold plate 16 such thatface 62 of closure plate 12 acts as a closure for coolant collectionpassages 44 and manifold means 58 in face 50 of manifold plate 16.Coolant flowing in manifold means 58 and coolant collection passages 44in manifold plate 16 simultaneously heats face 50 of manifold plate 16and face 62 of closure plate 12. Accordingly, manifold plate 16 isrelatively evenly heated by the heat which is transferred to face 51 bythe coolant flowing in manifold means 20'and coolant distributionpassages 26 in manifold plate 22 and by the heat which is transferred toface 50 by the coolant flowing in manifold means 58 and coolantcollection passages 44 in manifold plate 16. This even heating ofmanifold plate 16'helps minimize the thermal distortion of opticallyreflective face 40 of face plate 36 which would be caused by the uneventhermal expansion of face plate 36 relative to manifold plate 16'. Inlike manner, the heating of closure plate 12 by coolant flowing inmanifold means 58and coolant collectionpassages 44 in manifold plate 16helps minimize the thermal distortion of optically reflective face 40 offace plate 36 which would be caused by the uneven thermal expansion offace plate 36 relative to' closure plate 12.

Upper edge cover 64 and lower edge cover 66 close out the coolantpassages communicating with the upper and lower edges of manifold plates16 and '22 and face plate 36 such that there is no coolant flowcommunication between adjacent coolant passages. Instead of employingseparate edge covers, the upper and lower edges of manifold plates 16and 22 and face plate 36 7 may be electro-formed over to close out thecoolant passages contained therein.

Referring again to FIGS. 1 and 2, coolant enters inlet means 14inclosure plate 12 of mirror and is passed through inlet means 18 inmanifold plate 16 to manifold means 20 in manifold plate 22. Manifoldmeans 20 approximately equally distributes the inlet coolant flow toeach of coolant distribution passages 26 in manifold plate 22. Coolantdistribution passages 26 direct the coolant into coolant passages 34 inface plate 36. The coolant travels longitudinally and in oppositedirections in adjacent coolant passages 34 and is then led into coolantcollection passages 42 in manifold plate 22. Coolant collection passages42 direct the coolant to coolant collection passages 44 in manifoldplate 16. Coolant collection passages 44 direct the coolant intomanifold means 58 in manifold plate 16. The coolant is then passed bymanifold means 58 to exit means 60 in closure plate 12 where the coolantis discharged from mirror 10.

Referring now in detail to FIGS. 3 and 4, manifold plate 72 in mirror 70has inlet means 74, 76, 78 and 80, shown in the figure as hollow tubes,for the introduction of coolant into the coolant distribution network ofmirror 70. Inlet means 74 and 76 lead to manifold means 82 formed inupper side 84 of face 86 of manifold plate 72. Inlet means 78 and 80lead to manifold means 88 formed in lower side 90 of face 86 of manifoldplate 72. Manifold means 82 and 88 are in coolant flow communicationwith coolant distribution passages 92 in manifold plate 72. The exactshape of manifold means 82 and 88, shown as transverse channels, is notcritical except that the manifold means should approximatelyequally'distribute the inlet coolant flow to each of coolantdistribution passages 92.

Coolant distribution passages 92, shown as parallel, longitudinal,equally spaced slots, are formed in upper side 84 and lower side 90 offace 86 of manifold plate 72. The upper end of each of coolantdistribution passages 92 in upper side 84 and the lower end of each ofcoolant distribution passages 92 in lower side 90 extends throughmanifold plate 72 from face 86 to face 93. Coolant distribution passages92 are cut across or machined across upper and lower edges 94 and 95,respectively, of manifold plate 92. Each of the ends of coolantdistribution passages 92 extending through manifold plate 72 is matedwith and is in coolant flow communication with one of the ends of acoolant passage 96 in face plate 98. However, none of coolantdistribution passages 92 are in coolant flow communication with morethan one of coolant passages 96 in face plate 98.

Coolant passages 96, shown as parallel, longitudinal, equally spacedslots, are formed in face 100 of face plate 98. The exact shape andconfiguration of coolant passages 96 is not critical; however, coolantpassages 96should be arranged to evenly cool optically reflective face102 of face plate 98. Apertures 104, shown as circular holes, extendthrough face plate 98-and provide openings, for example, for thetransmission'of a laser beam from the interior of a laser opticalcavity.

Apertures 104 are shown positioned alongthe longituis in coolant flowcommunication of one of coolant distribution passages 92 and one ofcoolant collection passages 108 in manifold plate 72. One of eachadjacent pair of coolant passages 96 in face plate 98 is in Y coolantflow communication with a coolant distribution passage 92 in upper side84 and a coolant collection passage 108 in lower side of face 86 ofmanifold plate 72 and the other coolant passage of the adjacent pair ofcoolant passages 96 is in 'coolant flow communication with a coolantcollection passage 108 in upper side 84 and a coolant distributionpassage92 in lower side 90 of face 86 of manifold plate 72. Accordingly,coolant flow is countercurrent or, in other words, is in oppositedirections in adjacent coolant passages 96 in face plate 98.

Adjacent coolant distribution passages 92 and coolant collectionpassages 108 in manifold plate 72 are in coolant flow communication withthe ends of adjacent coolant passages 96 in face plate 98. Adjacentcoolant distribution passages 92 in manifold plate 72 are in coolantflow communication with the ends of subadjacent coolant passages 96 inface plate 98. In like manner, adjacent coolant collection passages 108in manifold plate 72 are in coolant flow communication with the ends ofsubadjacent coolant passages 96 in face plate 98. Face plate 98 isbonded to and mated with manifold plate 72 such that face 93 or manifoldplate 72 provides a closure forcoolant passages 96 in mirror face plate98. Heat is evenly distributed to face 93 of manifold plate 72 bycoolant flowing in coolant passages 96 in face plate 98. This evenheating of face 93 of manifold plate 72 helps minimize the thermaldistortion of optically reflective face 102 of face plate 98 which wouldbe caused by the uneven thermal expansion of face plate 98 relative tomanifold plate 72. Coolant is only communication between manifold plate72 and face plate 98 via coolant distribution passages 92 and coolantcollection passages 108 and the ends of coolant passages 96.

Coolant collection passages 108, shown as parallel, longitudinal,equally spaced slots, are formed in upper side 84 and lower side 90 offace 86 of manifold plate 72 and extend through manifold plate 72 fromface 86 to face 93. Coolant collection passages 108 are cut across ormachined across upper and lower edges 94 and 95, respectively, ofmanifold plate 7 2. a

One of each adjacent pair of coolant passages in manifold plate'72 is acoolant distribution passage 92 and the other coolant passage of eachadjacent pair is a coolant collection passage 108. Each coolantdistribution passage 92 in upper side 84 of face 86 of manifold plate 72is on the same longitudinal axis of face 86 of manifold plate 72 as acoolant collection passage 108 in lower side 90 of face 86 of manifoldplate 72. In like coolant distribution passage 92 in lower side 90 offace I 86 of manifold plate 72. Each of coolant collection passages 108in manifold plate 72 is in coolant flow communication with a coolantcollection passage 112 in manifold plate 114. Apertures 110, shown ascircular holes, extend through manifold plate 72 and are axially alignedand mated with apertures l0 4'in face plate 98 such that light can passthrough apertures 104 and then through apertures l 10.

Coolant collection passages 112, shown as parallel, longitudinal,equally spaced slots, are formed in upper side 116 and lower side 118 offace 120 of manifold plate 1 14. At least the upper end of each ofcoolant collection passages 112 in upper side 116 and at least the lowerend of each of coolant collection passages 112 in lower side 118 of faceof manifold plate 114 extends through. manifold plate 114 from face 120to face 121. Coolant collection passages 112 are shown as being cut ormachined across the upper and lower edges 122 and 123, respectively, ofmanifold plate 114. Each of the ends of coolant collection passages 112extending through manifold plate 114 is mated with and is in coolantflow communication with one of coolant collection passages 108 inmanifold plate 72. Each of coolant collection passages 112 in upper side116 of face 120 of manifold plate 114 is in coolant flow communicationwith one of coolant collection passages 108 in upper side 84 of face 86of manifold plate 72. In like manner, each of coolant collectionpassages 112 in lower side 118 of face 120 of manifold plate 114 is incoolant flow communication with one of coolant collection passages 108in lower side 90 of face 86 of manifold plate 72. Adjacent coolantcollection passages 112 in manifold plate 114 are in coolant flowcommunication with adjacent coolant collection passages 108 in manifoldplate 72.

The coolant collection passages 112 in upper side 116 of face 120 ofmanifold plate 114 are on the same longitudinal axis of face 120 ofmanifold plate 114 as the longitudinal center lines of the lands 124which which are formed by adjacent coolant collection passages 112 inlower side 118 of face 120 of manifold plate 114. In like manner, thecoolant collection passages 112 in lower side 118 of face 120 ofmanifold plate 114 are on the same longitudinal axis of face 120 ofmanifold plate 114 as the longitudinal center lines of the lands 125which are formed by adjacent coolant collection passages 112 in upperside 116 of face 120 of manifold plate 114.

Manifold plate 114 is bonded to and mated with manifold plate 72 suchthat face 121 of manifold plate 114 acts as a closure for manifold means82 and 88 and coolant distribution passages 92 in face 86 of manifoldplate 72. Coolant collection passages 112 in upper side 116 of face 120of manifold plate 114 are in flow communication with manifold means 126in manifoldplate 114. Coolant collection passages 112 in lower side 118of face 120 of manifold plate 114 are in coolant flow communication withmanifold means 127 in manifold plate 114. Manifold means 126 and 127,shown as transverse channels, are formed in upper side 116 and lowerside 118, respectively, of face 120 of manifold plate 114. The exactshape of manifold means 126 and 127 is not critical except that manifoldmeans 126 and 127 should collect coolant from each of coolant collectionpassages 112 and conduct this coolant to the appropriate exit means.Exit means 128 and 130, shown as hollow tubes, discharge coolant frommanifold means 126 and exit means 132 and 134, shown as hol low tubes,discharge coolant from manifold means 127. Manifold plate 114 containsaperture 135, shown as a rectangular opening, extending through manifoldplate 114 to allow light exiting from apertures 110 in manifold plate 72to pass through manifold plate 114.

means 126 and 127 in face of manifold plate 114. a

Closure plate 136 contains-aperture 140, shown as a rectangular opening,extending through closure plate 136 to allow light exiting fromapertures 110. in manifold plate 72 to pass through closure plate 136.

Upper edge cover 142 and lower edge cover 144 close out the coolantpassages communicating with the upper and lower edges of manifold plates72 and 114 and face plate 98 such that there is no coolant flowcommunication between adjacent coolant passages. Instead of employingseparate edge covers, the upper and lower edges of manifold plates 72and 114 and face plate 98 may be electroformed over to close out thecoolant passages contained therein.

It should be noted that, for the sake of clarity, the same number ofcoolant passages have not been shown in the manifold plates and faceplate of FIG. 3 as have been shown in the manifold plates and face plateof FIG. 4. Otherwise, however, the mirrors of FIGS. 3 and 4 correspond.

Referring again to FIGS. 3 and 4, coolant enters manifold means 82 inmanifold plate 72 via inlet means 74 and 76 and manifold means 88 inmanifold plate 72 via inlet means 78 and 80. Manifold means 82 and 88approximately equally distribute the inlet coolant flow to each ofcoolant distribution passages 92 in manifold plate 72. Coolantdistribution passages 92 direct the coolant into coolant passages 96 inface plate 98. The coolant travels longitudinally and in oppositedirections in adjacent coolant passages 96 and is then led into coolantcollection passages 108 in manifold plate 72. Coolant collectionpassages 108 direct the coolant to coolant collection passages 112 inmanifold plate 114. Coolant collection passages 112 direct the coolantinto manifold means 126 and 127 in manifold plate 114. The coolant isthen passed by manifold means 126 to exit means 128 and 130 and bymanifold means 127 to exit means 132 and 134 where the coolant isdischarged from mirror 70.

The mirrors of the present invention are formed from suitable materials,preferably highly heat-conductive metals such as nickel andberyllium-copper alloys. The coolant passages are formed in the face andmanifold plates by conventional technique, such as by machining. Thecoolant employed may be any conventional material such as water. Thebonding together of the face, manifold and closure plates is conductedin known manner, such as by diffusion bonding, and the opticallyreflective surface of the mirror is formed by techniques which areconventional in the art. For example, once the mirror has been assembledand the face, manifold and closure plates mated and bonded together, anickel layer of approximately 2 to 3 mil thickness is applied to theface of the face plate which is to be the optically reflective surfaceand lapped or polished to approximately 0.5 to 1 mil thickness. A 2 to 3mil thick silver layer is then applied to the nickel layer and lapped orpolished to approximately 0.5 to 1 mil thickness. Finally, a l milthickmagnesium fluoride layer is applied to the silver layer and lapped orpolished to approximately 0.5 mil thickness.

FIGS. 1 and 2 can be used in conjunction with the partially transmissivemirror of FIGS. 3 and 4 in a conventional laser optical cavity.

We claim:

1. A mirror comprising a first component having coolant distribution andcollection passages and manifold means for receiving and distributingcoolant to each of said coolant distribution passages, a secondcomponent having an optically reflective surface and coolant passages inheat-exchanging relationship with said optically reflective surface,each of the coolant passages in said second component extending so as toaccord a single heat-exchanging pass across said reflective surface andbeing in coolant flow communication with one of the coolant distributionand one of the coolant collection passages in said first component and athird component having coolant collection passages and manifold meansfor collecting coolant from each of the coolant collection passages insaid third component and for discharging coolant from said mirror, thecoolant collection passages in said third component being in coolantflow communication with the coolant collection passages in said firstcomponent.

2. The mirror of claim 1 in which the coolant distribution andcollection passages in the first component are in coolant flowcommunication with the ends of the coolant passages in the secondcomponent.

3. The mirror of claim 2 in which the coolant passages in the secondcomponent are substantially parallel and one end of each adjacent pairof ends of said coolant passages is in coolant flow communication with acoolant distribution passage in the first component and the other end ofsaid adjacent pair of ends is in coolant flow communication with acoolant collec-. tion passage in said first component such that coolantflow is in opposite directions in each adjacent pair of coolant passagesin said second component.

4. The mirror of claim 3 in which the coolant distribution andcollection passages in the first component are substantially paralleland each adjacent pair of coolant passages in saidfirst component iscomposed of a coolant distribution passage and a coolant collectionpassage. I

5. The mirror of claim 4 in which adjacent coolant passages in'the firstcomponent are in coolant flow communication with adjacent coolantpassages in the second component.

6. A mirror comprising:

A. a first manifold plate having first and second faces, coolantdistribution and collection passages formed in said first face, at leasta portion of each of said coolant distribution and collection passagesextending through said first manifold plate from said first face to saidsecond face and manifold means formed in said first face for receivingand distributing coolant to each of said coolant distribution. passages;

12 B. a face plate having first and second faces, coolant passagesformed in and making a single pass across said first face and anoptically reflective surface formed on said second face, the coolantpassages: and the optically reflective surface in said face? plate beingin heat-exchanging relationship, said face plate being mated with saidfirst manifold plate such that the coolant passages in said face plateare in coolant flow communication with the portions of the coolantdistribution and collection passages extending through said firstmanifold plate and such that the second face of said first manifoldplate acts as a closure for the coolant passages in the first face ofsaid face plate, each of the coolant passages in said face plate beingin coolant flow communication with one of the coolant distribution andone of the coolant collection passages in said first manifold plate; C.a second manifold plate having first and second faces, coolantcollection passages formed in said first face, at least a portion ofeach of the coolant collection passages in said first face extendingthrough said second manifold plate from said first face to said secondface and manifold 'means formed in said first face for collectingcoolant from each of the coolant collection passages in said secondmanifold plate and for discharging coolant from said mirror, said secondmanifold plate being mated with said first manifold plate such that theportions of the coolant collection passages extending through saidsecond manifold plate are in coolant flow communication with thecoolant'collection passages in said first manifold plate and such thatthe second face of said second manifold plate acts as a closure for thecoolant passages and manifold means in the first face of said firstmanifold plate; and D. closure means for the coolant collection passagesand manifold means in the first face of said second manifold plate. v 7.The mirror of claim 6 in which the first face of the first manifoldplate has first and second sides, the coolant distribution andcollection passages in said first face are substantially parallel andare formed in each of said first and second sides-0f said first face andeach adjacent pair of coolant passages in said first manifold plate iscomposed of a coolant distribution passage and a coolant collectionpassage. I

8. The mirror of claim 7 in which the coolant passages in the face plateare substantially parallel and one of each adjacent pair of coolantpassages in said face plate is in coolant flow communication with acoolant distribution passage in the first sideand a coolant collectionpassage in the second side of the first face of the first manifold plateand the other coolant passage of said adjacent pair is in flowcommunication with a coolant collection passage in said first side and acoolant distribution passage in said second side of said first face ofsaid first manifold plate such that coolant flow is in oppositedirections in each adjacent pair of coolant passages in said face plate.

9. The mirror of claim 8 in which adjacent coolant passages in the faceplate are in coolant flow communication with adjacent coolant passagesin thefirst manifold plate.

10. The mirror of claim 9 in which the first face of the second manifoldplate has first and second sides and the coolant collection passages insaid first face are substantially parallel and are formed in each ofsaid first and second sides of said first face.

11. The mirror of claim 6 in which the mirror is one of the mirrors of alaser optical cavity.

12. A thermally compensated mirror comprising a leafed structure having:

a first plate having an optically reflective outer surface and coolantpassageways within the plate, each passageway providing for at least asingle pass of a fluid in heat-exchanging relationship with saidreflective outer surface;

an inlet plate situated behind the side of said first plate which isopposite the reflective outer surface, said inlet plate having coolantdistribution and collection passageways communicating with the coolantpassageways in said first plate;

an exit manifold plate situated behind the side of said inlet platewhich is remote from said first plate for discharging heated fluid, saidexit manifold plate having an exit manifold communicating with the fluidinput means connected to supply coolant to said 7 coolant distributionpassageways of said inlet plate v whereby, in operation, thermaldistortion between said optically reflective outer surface of said firstplate and said exit manifold plate is minimized. 13. The mirror of claim12, wherein: said passageways are formed in the surfaces of said plates;and said plates are secured in contiguous relation such that the surfaceof each plate serves to close the passageways in each adjacent plate.14. The mirror of claim 12, wherein: two sets of said coolantpassageways are formed in said first plate, and the direction of flow ofcoolant through each of said coolant passageways is counter to the flowof coolant through each adjacent coolant passageway.

1. A mirror comprising a first component having coolant distribution andcollection passages and manifold means for receiving and distributingcoolant to each of said coolant distribution passages, a secondcomponent having an optically reflective surface and coolant passages inheat-exchanging relationship with said optically reflective surface,each of the coolant passages in said second component extending so as toaccord a single heat-exchanging pass across said reflective surface andbeing in coolant flow communication with one of the coolant distributionand one of the coolant collection passages in said first component and athird component having coolant collection passages and manifold meansfor collecting coolant from each of the coolant collection passages insaid third component and for discharging coolant from said mirror, thecoolant collection passages in said third component being in coolantflow communication with the coolant collection passages in said firstcomponent.
 2. The mirror of claim 1 in which the coolant distributionand collection passages in the first component are in coolant flowcommunication with the ends of the coolant passages in the secondcomponent.
 3. The mirror of claim 2 in which the coolant passages in thesecond component are substantially parallel and one end of each adjacentpair of ends of said coolant passages is in coolant flow communicationwith a coolant distribution passage in the first component and the otherend of said adjacent pair of ends is in coolant flow communication witha coolant collection passage in said first component such that coolantflow is in opposite directions in each adjacent pair of coolant passagesin said second component.
 4. The mirror of claim 3 in which the coolantdistribution and collection passages in the first component aresubstantially parallel and each adjacent pair of coolant passages insaid first component is composed of a coolant distribution passage and acoolant collection passage.
 5. The mirror of claim 4 in which adjacentcoolant passages in the first component are in coolant flowcommunication with adjacent coolant passages in the second component. 6.A mirror comprising: A. a first manifold plate having first and secondfaces, coolant distribution and collection passages formed in said firstface, at least a portion of each of said coolant distribution andcollection passages extending through said first manifold plate fromsaid first face to said second face and manifold means formed in saidfirst face for receiving and distributing coolant to each of saidcoolant distribution passages; B. a face plate having first and secondfaces, coolant passages formed in and making a single pass across saidfirst face and an optically reflective surface formed on said secondface, the coolant passages and the optically reflective surface in saidface plate being in heat-exchanging relationship, said face plate beingmated with said first manifold plate such that the coolant passages insaid face plate are in coolant flow communication with the portions ofthe coolant distribution and collection passages extending through saidfirst manifold plate and such that the second face of said firstmanifold plate acts as a closure for the coolant passages in the firstface of said face plate, each of the coolant passages in said face platebeing in coolant flow communication with one of the coolant distributionand one of the coolant collection passages in said first manifold plate;C. a second manifold plate having first and second faces, coolantcollection passages formed in said first face, at least a portion ofeach of the coolant collection passages in said first face extendingthrough said second manifold plate from said first face To said secondface and manifold means formed in said first face for collecting coolantfrom each of the coolant collection passages in said second manifoldplate and for discharging coolant from said mirror, said second manifoldplate being mated with said first manifold plate such that the portionsof the coolant collection passages extending through said secondmanifold plate are in coolant flow communication with the coolantcollection passages in said first manifold plate and such that thesecond face of said second manifold plate acts as a closure for thecoolant passages and manifold means in the first face of said firstmanifold plate; and D. closure means for the coolant collection passagesand manifold means in the first face of said second manifold plate. 7.The mirror of claim 6 in which the first face of the first manifoldplate has first and second sides, the coolant distribution andcollection passages in said first face are substantially parallel andare formed in each of said first and second sides of said first face andeach adjacent pair of coolant passages in said first manifold plate iscomposed of a coolant distribution passage and a coolant collectionpassage.
 8. The mirror of claim 7 in which the coolant passages in theface plate are substantially parallel and one of each adjacent pair ofcoolant passages in said face plate is in coolant flow communicationwith a coolant distribution passage in the first side and a coolantcollection passage in the second side of the first face of the firstmanifold plate and the other coolant passage of said adjacent pair is inflow communication with a coolant collection passage in said first sideand a coolant distribution passage in said second side of said firstface of said first manifold plate such that coolant flow is in oppositedirections in each adjacent pair of coolant passages in said face plate.9. The mirror of claim 8 in which adjacent coolant passages in the faceplate are in coolant flow communication with adjacent coolant passagesin the first manifold plate.
 10. The mirror of claim 9 in which thefirst face of the second manifold plate has first and second sides andthe coolant collection passages in said first face are substantiallyparallel and are formed in each of said first and second sides of saidfirst face.
 11. The mirror of claim 6 in which the mirror is one of themirrors of a laser ''''optical cavity.''''
 12. A thermally compensatedmirror comprising a leafed structure having: a first plate having anoptically reflective outer surface and coolant passageways within theplate, each passageway providing for at least a single pass of a fluidin heat-exchanging relationship with said reflective outer surface; aninlet plate situated behind the side of said first plate which isopposite the reflective outer surface, said inlet plate having coolantdistribution and collection passageways communicating with the coolantpassageways in said first plate; an exit manifold plate situated behindthe side of said inlet plate which is remote from said first plate fordischarging heated fluid, said exit manifold plate having an exitmanifold communicating with the collection passageways of said inletplate and with a fluid discharge means; and fluid input means connectedto supply coolant to said coolant distribution passageways of said inletplate whereby, in operation, thermal distortion between said opticallyreflective outer surface of said first plate and said exit manifoldplate is minimized.
 13. The mirror of claim 12, wherein: saidpassageways are formed in the surfaces of said plates; and said platesare secured in contiguous relation such that the surface of each plateserves to close the passageways in each adjacent plate.
 14. The mirrorof claim 12, wherein: two sets of said coolant passageways are formed insaid first plate, and the direction of flow of coolant through each ofsaid coolant passageways is counter to the Flow of coolant through eachadjacent coolant passageway.